Electrical coil insulated with shellac and cashew nut shell liquid reaction product



Patented Dec. 17, 1940 UNITED STATES.

PATENT OFFICE ELECTRICAL COIL INSULATED WITH SHEL- LAC AND CASHEW NUT SHELL LIQUID REACTION PRODUCT No Drawing. Application December 1, 1938,

Serial No.

1 Claim.

The present invention relates to method and steps for forming an electrical conductor and aninsulating material into a coiled unit which is solid in part or substantially throughout and which will withstand mechanical pressure due to its own weight and to other causes, which will remain solid at elevated temperatures and which will resist the action of solvents and chemicals.

Heretofore, solid coiled units of conductor and insulation have been formed by dipping an insulated coil into an impregnation bath of a solvent which carries a material adapted to be set to a hardness which will hold the turns of the coil securely together and to be an insulator whereby the coil is thoroughly impregnated and saturated with the solution, and then heating to drive off the solvent and to set the material carried by said solvent into a dried and hardened state. But there have always been attending disadvantages which result because it is diflicult to remove the solvent from the inner parts or layers of the coil. And this difficulty is increased because the solvent leaves the surface and adjacent parts of the coil rather readily and before it leaves the inner parts of the coil with the result that at the surface the material left by the solvent is set and forms a seal which traps that part of the solvent which is still within the coil and keeps it there whereby the material carried thereby is prevented from becoming set and from acquiring the desired insulating characteristics. Also any heating beyond given limits results in expansion of the solvent and in distortion or even blowing out of the coil.

It is therefore an object of the present invention to provide methods and steps of applying an insulating material to a conductor and subsequently forming a coil therefrom, either after, removing any solvent used for applying the insulating and bonding material or entirely without the use of solvent.

Another object of the present invention is to provide a method whereby an integral insulated coil can be formed from a coated conductor without the use of any solvent in the making of the coil itself, although a solvent may have been used to apply the coating material to the wire and removed before the coated wire is formed into a coil.

Another object of the present invention is to provide a method of coating a conductor with a bonding material which, in the absence of a solvent, is flexible and is capable of bonding with itself and yet has enough body so that it will not how unduly when the conductor to which it is applied is formed into a coil and which can be thermoset to transform the self-bonded material into a state in which it is insoluble and infusible at predetermined temperatures.

Another object of the present invention is to 5 provide a method having the advantages above set forth when used on a conductor which has a preliminary or primary coating of insulating enamel and by which method a bonding material is applied with a solvent vehicle which will not cut or deleteriously afiect said enamel before the said solvent vehicle can be removed from the applied bonding material.

In the appended claims the term infusible is intended to mean both infusibility at higher temperatures up to the carbonizing point or disintegrating point and infusibility at the temperature at which the prepared coil is baked, the object being to render the coating impregnating material infusible or non-thermo-plastic at temperago tures to which it may be subjected while in use as well as to render it resistant to solvents, whereby the coil will be held in its desired form and shape at all operating temperatures and at temperatures sufliciently higher to provide a suit- 5 able safety factor and this due to the implasticity or infusibility of the coating or impregnating material.

The insulating practice of the present invention is suitable for bare conductor, for enameled con- 3 ductors, for conductors covered as, for example, with a cotton braid, for conductors which have been enameled and then covered with a braid and for use generally for making coils or a multiplicity of turns or layers of either rigid bars or flexible wires.

Emmple.--An illustrative example of a material suitable for the practice of the present invention is as follows: Equal parts by weight of shellac (e. g., delta shellac) and the residue ob- 4 tained by distilling cashew nut shell liquid with steam to remove about fifty per cent of the weight of the cashew nut shell liquid are heated together to about 150 C. whereupon application of heat is discontinued. The temperature will rise about five degrees and the material is stirred thoroughly, poured into hollow pans and, when cooled, broken up and pulverized.

The cashew nut shell liquid residue is a'mixture of phenols and distillation residues and appears to contain some heat polymerization products, that is polymerized phenols and is solid when cold and can be softened with heat.

The cashew nut shell liquid residue-shellac product made as described above and pulverized can be dissolved cold in a mixture of equal parts of normal butyl alcohol and toluol to the extent of about 47% solids, and this solution can be thinned with high flash naphtha, for example, six parts of said solution and about one part 'of high flash naphtha, by weight.

This material can be applied to bare, enameled, braided, or enameled and braided wire by running the wire through the solution to pick up a coating and running the coated wire through an oven at about 120 C., at a rate that will give the coated wire a. heating for one minute, that is, e. g, at the rate of six feet per minute through an oven which is six feet long and is at about 120 C. (250 F. to 260 F.). This coated wire is then wound tightly into coils and baked at about 120 C. for about 20 hours during which the coating material softens and forms an integral mass which binds the coil of wire together. This heating also gradually brings about a setting of the material to a. state in which it is infusible at the baking temperature and also at higher temperatures, high enough to prevent softening of the binder at temperatures which will give a substantial safety factor for temperatures above normal operating temperatures.

Having thus described my invention, what I claim and desire to protect by Letters Patent is:

An electrically insulated wound coil having adjacent turns separated from each other and supported to each other by a unitary mass of solvent free infusible heat reaction product of shellac and cashew nut shell liquid distillation residue which said reaction product has been transformed in situ in said coil from the fusible state to a substantially infusible state.

JOHN J. CONNORS. 

